Kaitlyn builds a project in which light bulb A and light bulb B are in parallel circuits. The project has a switch and uses a battery for its source of voltage. She connects her battery and neither light turns on. Which of the following could possibly be the problem with her project?

a. Light bulb A is broken.

b. Light bulb B is broken

c. The switch is not closed

d. Any of these would cause the problem described